DETROIT -- The battle for minivan supremacy is turning into a horse race.

The Toyota Sienna may win its first sales title in the segment.

At the end of the year, win, place and show likely will be determined by parts availability, end-of-year consumer deals and possibly a fleet transaction. Through the end of October a mere 975 vehicles separated first and second place.

Here are the numbers:

Through October, the Dodge Grand Caravan was first, recording 92,930 sales. Running a very close second was the Sienna with 91,955.

In third place was the Honda Odyssey with 86,436 units. A distant fourth was the Chrysler Town & Country, 78,255.

Here are the factors that could determine this year's minivan sales champion.

n Parts availability: Honda and Toyota have said that the March earthquake and tsunami reduced production capacity -- and that includes minivans. Toyota adds that the flooding in Thailand is affecting current Sienna production.

Unclear is what components Toyota might be able to switch, say from the Camry or other models to the Sienna, if the Toyota entry has a shot at the minivan sales title.

n Deal of the month: My guess is that if the Grand Caravan and Sienna are running neck and neck as they approach the finish line, one or both will come up with a sweet retail deal. Again, that's assuming Toyota comes up with the parts for a sales battle to the end.